[Wi-Fi] [a11y] In Wi-Fi data usage page, Talkback should also announce the Progress bar percentage instead of "Progress bar" only.

Add conent description for talkback to announce, if the progress bar is 50%, then before modification is "Progress bar", and after modification is "50% Progress bar".

Bug: 146811265
Test: Add following unit test case to test if content description is correct or not:
      createPref_progressBarShouldSetPercentageContentDescription().

Change-Id: I71483df8e12f08c4c8c96ab3964666bf97872a83

src/com/android/settings/datausage/AppDataUsagePreference.java

@@ -26,6 +26,8 @@ import com.android.settingslib.net.UidDetailProvider;
 import com.android.settingslib.utils.ThreadUtils;
 import com.android.settingslib.widget.apppreference.AppPreference;
 
+import java.text.NumberFormat;
+
 public class AppDataUsagePreference extends AppPreference {
 
     private final AppItem mItem;
@@ -66,6 +68,8 @@ public class AppDataUsagePreference extends AppPreference {
             progress.setVisibility(View.VISIBLE);
         }
         progress.setProgress(mPercent);
+        progress.setContentDescription(
+                NumberFormat.getPercentInstance().format((double) mPercent / 100));
     }
 
     private void setAppInfo() {

tests/robotests/src/com/android/settings/datausage/AppDataUsagePreferenceTest.java

@@ -22,6 +22,11 @@ import static org.mockito.Mockito.when;
 
 import android.graphics.Color;
 import android.graphics.drawable.ColorDrawable;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.widget.ProgressBar;
+
+import androidx.preference.PreferenceViewHolder;
 
 import com.android.settingslib.AppItem;
 import com.android.settingslib.net.UidDetail;
@@ -37,6 +42,7 @@ import org.robolectric.RuntimeEnvironment;
 
 @RunWith(RobolectricTestRunner.class)
 public class AppDataUsagePreferenceTest {
+    private static final String FIFTY_PERCENT = "50%";
 
     @Mock
     private UidDetailProvider mUidDetailProvider;
@@ -77,4 +83,22 @@ public class AppDataUsagePreferenceTest {
         assertThat(mPreference.getTitle()).isEqualTo(mUidDetail.label);
         assertThat(mPreference.getIcon()).isEqualTo(mUidDetail.icon);
     }
+
+    @Test
+    public void createPref_progressBarShouldSetPercentageContentDescription() {
+        when(mUidDetailProvider.getUidDetail(mAppItem.key, true /* blocking */))
+                .thenReturn(mUidDetail);
+        mPreference = new AppDataUsagePreference(RuntimeEnvironment.application, mAppItem,
+                50 /* percent */, mUidDetailProvider);
+        final View view = LayoutInflater.from(RuntimeEnvironment.application).inflate(
+                com.android.settingslib.R.layout.preference_app, null);
+        final PreferenceViewHolder preferenceViewHolder =
+                PreferenceViewHolder.createInstanceForTests(view);
+        final ProgressBar progressBar = (ProgressBar) preferenceViewHolder.findViewById(
+                android.R.id.progress);
+
+        mPreference.onBindViewHolder(preferenceViewHolder);
+
+        assertThat(progressBar.getContentDescription()).isEqualTo(FIFTY_PERCENT);
+    }
 }